The present invention relates to a method of cleaning using partially fluorinated ethers having a tertiary structure.
Vapor degreasing and solvent cleaning with fluorocarbon based solvents have found widespread use in industry for the degreasing and otherwise cleaning of solid surfaces, especially intricate parts and difficult to remove soils.
In its simplest form, vapor degreasing or solvent cleaning consists of exposing a room-temperature object to be cleaned to the vapors of a boiling solvent. Vapors condensing on the object provide clean distilled solvent to wash away grease or other contamination. Final evaporation of solvent from the object leaves behind no residue as would be the case where the object is simply washed in liquid solvent.
For soils which are difficult to remove, where elevated temperature is necessary to improve the cleaning action of the solvent, or for large volume assembly line operations where the cleaning of metal parts and assemblies must be done efficiently and quickly, the conventional operation of a vapor degreaser consists of immersing the part to be cleaned in a sump of boiling solvent which removes the bulk of the soil, thereafter immersing the part in a sump containing freshly distilled solvent near room temperature, and finally exposing the part to solvent vapors over the boiling sump which condense on the cleaned part. In addition, the part can also be sprayed with distilled solvent before final rinsing.
Vapor degreasers suitable in the above-described operations are well known in the art. For example, Sherliker et al. in U.S. Pat. No. 3,085,918 disclose such suitable vapor degreasers comprising a boiling sump, a clean sump, a water separator, and other ancilliary equipment.
Cold cleaning is another application where a number of solvents are used. In most cold cleaning applications, the soiled part is either immersed in the fluid or wiped with rags or similar objects soaked in solvents.
In cold cleaning applications, the use of the aerosol packaging concept has long been found to be a convenient and cost effective means of dispensing solvents. Aerosol products utilize a propellant gas or mixture of propellant gases, preferably in a liquefied gas rather than a compressed gas state, to generate sufficient pressure to expel the active ingredients, i.e. product concentrates such as solvents, from the container upon opening of the aerosol valve. The propellants may be in direct contact with the solvent, as in most conventional aerosol systems, or may be isolated from the solvent, as in barrier-type aerosol systems.
Chlorofluorocarbon solvents, such as trichlorotrifluoroethane, have attained widespread use in recent years as effective, nontoxic, and nonflammable agents useful in degreasing applications and other solvent cleaning applications. Trichlorotrifluoroethane has been found to have satisfactory solvent power for greases, oils, waxes and the like. It has therefore found widespread use for cleaning electric motors, compressors, heavy metal parts, delicate precision metal parts, printed circuit boards, gyroscopes, guidance systems, aerospace and missile hardware, aluminum parts and the like. Trichlorotrifluoroethane has two isomers: 1,1,2-trichloro-1,2,2-trifluoroethane (known in the art as CFC-113) and 1,1,1-trichloro-2,2,2-trifluoroethane (known in the art as CFC-113a). CFC-113 has a boiling point of about 470.degree. C. and has been found to have satisfactory solvent power for greases, oils, waxes, and the like.
Another commonly used solvent is chloroform (known in the art as HCC-20) which has a boiling point of about 630.degree. C. Perchloroethylene is a commonly used dry cleaning and vapor degreasing solvent which has a boiling point of about 1210.degree. C. These compounds are disadvantageous for use as solvents because they are toxic; also, chloroform causes liver damage when inhaled in excess.
Although chlorine is known to contribute to the solvency capability of a compound, fully halogenated chlorofluorocarbons are suspected of causing environmental problems in connection with the earth's protective ozone layer. Thus, the art is seeking new compounds which do not contribute to environmental problems but yet provide the solvency properties of CFC-113.
Azeotropic compositions having non-tertiary partially halogenated ethers therein are known in the art. For example, U.S. Pat. No. 4,999,127 teaches azeotropic compositions of 2-chloro-1,1,2-trifluoroethyl-2-difluoromethyl ether, trans-1,2dichloroethylene, and methanol which are useful as solvents. U.S. Pat. No. 5,023,009 teaches azeotropic compositions of 1,1,1,2,3,3-hexafluoro-3-methoxypropane and 2,2,3,3,3-pentafluoropropanol-1. U.S. Pat. No. 5,023,010 teaches azeotropic compositions of 1,1,1,2,3,3-hexafluoro-3-methoxypropane and methanol, isopropanol, or n-propanol. U.S. Pat. No. 5,026,498 teaches azeotropic compositions of 1,1,1,2,3,3-hexafluoro-3-methoxypropane and trans-1,2dichloroethylene, cis-1,2-dichloroethylene, 1,1-dichloro-1,2-difluoroethane, or 1,2-dichloro-1,2difluoroethane.
It would be advantageous to have solvents with improved solvency characteristics compared with 1,1,1,2,3,3-hexafluoro-3-methoxypropane.
A wide variety of consumer parts is produced on an annual basis in the United States and abroad. Many of these parts have to be cleaned during various manufacturing stages in order to remove undesirable contaminants. These parts are produced in large quantities and as a result, substantial quantities of solvents are used to clean them.
Thus, solvents with improved solvency characteristics and which are negligible contributors to ozone depletion and to greenhouse warming are needed in the art.